<template>
  <h2>子级组件</h2>
  <h3>age:{{ age }}</h3>
  <h3>length:{{ length }}</h3>
</template>

<script lang="ts">
import { defineComponent, Ref, computed, toRef } from 'vue'
function useGetLength(age: Ref) {
  return computed(() => {
    return age.value.toString().length
  })
}
export default defineComponent({
  props: {
    age: {
      type: Number,
      require: true
    }
  },
  name: 'Child',
  setup(props) {
    let length = useGetLength(toRef(props, 'age'))
    return {
      length
    }
  }
})
</script>

<style scoped>
</style>